1. Technical Field
The present invention relates to a liquid ejecting head unit and a liquid ejecting apparatus, which eject liquid droplets, and in particular, relates to an ink jet recording head and an ink jet recording apparatus, which eject ink droplets as the liquid droplets.
2. Related Art
A liquid ejecting apparatus represented by an ink jet recording apparatus such as an ink jet printer and an ink jet plotter includes a liquid ejecting head unit in which a plurality of liquid ejecting heads are provided. The liquid ejecting heads are capable of ejecting, from nozzles, a liquid such as ink reserved in a cartridge, a tank or the like.
The plurality of liquid ejecting heads which configure the liquid ejecting head unit as described above are fixed at predetermined positions of a base plate as a holding member common thereto in a state being positioned with high accuracy. Specifically, the respective liquid ejecting heads are fixed to the base plate in a state where the respective nozzles thereof are positioned with high accuracy. For example, the respective liquid ejecting heads are fixed to the based plate while being positioned with high accuracy so that the plurality of nozzles of the respective liquid ejecting heads may be aligned with one another continuously at a constant pitch in the direction along a nozzle array in which the plurality of nozzles are arrayed.
As a method for positioning the liquid ejecting heads, for example, there is a method of attaching sub units (corresponding to the liquid ejecting heads) onto an alignment substrate (corresponding to the base plate), which is formed of a silicon substrate, while positioning the sub units at predetermined positions on the alignment substrate. Here, such attachment and positioning are performed in such a manner that a key groove and keys are formed by photolithography on the alignment substrate and the sub units, respectively, and the keys are engaged with the key groove. Japanese Patent No. 2,549,762 is an example of this related art.
The respective liquid ejecting heads may be fixed to the base plate while being positioned with high accuracy using the method as described above. However, even if the liquid ejecting heads are positioned to a member such as the silicon substrate capable of positioning with high accuracy using the keys and the key groove as in Japanese Patent No. 2549762, it may be difficult to position the liquid ejecting heads with high accuracy.
For example, in the case where a failure has occurred in one liquid ejecting head in the liquid ejecting head unit including the plurality of liquid ejecting heads, it is not necessary to replace the entirety of the liquid ejecting head unit, but the one liquid ejecting head in which the failure has occurred just needs to be replaced. Therefore, if the liquid ejecting head unit is used for a long period, then attachment and detachment of the liquid ejecting heads to and from the base plate are repeated.
If the attachment and detachment of the liquid ejecting heads to and from the base plate are repeated as described above, then there arises a risk that, for example, such a problem may occur that the keys and the key groove provided on the member formed of the silicon substrate become chipped. Therefore, it should be understood that positional accuracy of the liquid ejecting heads to the base plate may be lowered, resulting in lowering of accuracy in target positions of liquid droplets.
Such a problem exists not only in the member formed of the silicon substrate but also commonly in general positioning members. For example, there is apprehension that positioning portions of the base plate may be worn in that the attachment and detachment of the liquid ejecting heads to and from the base plate are repeated, resulting in lowering of the positional accuracy.
Note that such a problem exists not only in the ink jet recording head unit but also, in a similar way, in a liquid ejecting head unit that ejects a liquid other than ink.